Signal separation



A K. SCHLESINGER July 3l, 1951 SIGNAL SEPARATION 2 Sheets-Sheet l Fileds ept. 18; 1946 www,

July 31, 1951 I K. scHLEsANGER 2,562,216

SIGNAL SEPARATION 'Filed sept. 18, 1946 2 sheets-sheet 2 AA AA AA AA AAP-Hm- %Ho|5 5046.5 Aon ANVENTOR KURT SCHLESINGER @LA @.Zfwyw ATTORNEYPatented July 31, L1951 SIGNAL SEPARATION Kurt Schlesinger, New York, N.Y., assignor to Columbia Broadcasting System, Inc., New York, N. Y., acorporation of New York Application September 18, 1946, Serial No.697,721

I'his invention relates primarily to television, particularly colortelevision, and is especially dedesigned to provide a method andapparatus for separating color synchronizing signals from othersynchronizing signals in a color television signal. However, in itsbroader aspects the inventionis more Widely applicable. l

For convenience of explanation, the invention will be describedprimarily as it is used in a color television system. The more generalapplications will be apparent to those in the art, but will be pointedout briefly hereinafter.

The transmission of color pictures by television has been developedthrough the use of combinations of signals representing the primarycolors, red, green, and blue. One successful system utilizes repeatedfield scansions of the scene to be transmitted through a predeterminedsequence of color filters, with the resultant signals reproduced at thereceiving end sequentially through iilters of corresponding colors. Thecolor filters required are commonly rotated mechanically into properposition. Such lters are usually mounted ina color wheel, which may havethe form of a disk, cylinder, or truncated cone, for` example.

Synchronization of the line and field scanning at a televisiontransmitter and receiver has been accomplished by a number of circuitmeans Well known in the art. In color television it will be appreciatedthat it is essential, in addition, to insure that the groups of signalsrepresenting scansions in each of theprimary colors, called the colorfield, are properly synchronized with the movements of the color lterWheel. This synchronization must be eifective not only in propersequence and rate of `change of the primary colors, but also in phase sothat a reproduced eld representing the red aspect of a scene will bereproduced through a red lter, etc.

' Field synchronizing signals have been employed for synchronizing thecolor lter Wheel at a receiver With that at the transmitter. With suchsynchronization areproduced field correspondingfto',

one color aspect of a scene, say red, may be reproduced through a greenor blue filter, so that provision is made for the operator to change thephase of the color Wheel at the receiver until red aspects are exhibitedthrough'red filters, greenr aspects through green Ilters, etc. This maybe termed color phasing. v A j f It is advantageous to effect the colorphasing automatically. It has thereforebeen suggested to transmitdistinctive color synchronizing signals for this purpose. Such colorsynchronizingl signals may be used by themselves to eifect 'syn- 21clanes..V (ci. rvs-5.4)

chronization, or may be used in conjunction With field synchronizingsignals.

Examples of various types of synchronization are contained in U. S.Patents Nos. 2,329,194 and 2,323,905 to Goldmark, and 2,319,789 toChambers.V While theoretically many different types of distinctive colorsynchronizing signals are possible, in' practice it is advantageous toemploy as simple signals as possible and to avoid increasing'the bandWidth of the over-all television signal. Commonly, line synchronizationis accomplished by single pulses transmitted between successive linescansions, and eld synchronization is accomplished by a group ofalternate short and long pulses transmitted between successive fieldscansions. It has been proposed to employ a group of short pulses as acolor synchronizing signal.l For a three-color system such a group ofshort pulses would be transmitted during the blanking interval afterevery third field, thusalways being associated with the same colorfield. Such a color synchronizing signal presents the problem ofseparating it from the field synchronizing signal. The harmonic contentof the color synchronizing sig-j nal may not be suiciently differentfrom that ofl the eld synchronizing signal to enable separation byfrequency discrimination with suiviicient reliability. It will, ofcourse, be realized that reliability of color synchronization, and hencethe' reliability of the separation of color and eld synchronizingsignals, is of great importance in a practical color television system.

It is a particular object of the present inven-` tion to provide amethod and apparatus which permits the reliable separation of the colorsynchronizing signal so that correct color synchroni-` zation isobtained. i While not conned thereto, for convenience the invention willbe described in connection With a multiplex type of transmission, inwhich the video," sound, and line, eld, and color synchronizing sig'-nals are transmitted on the same carrier and separated at the receiverby suitable circuit means. y

The field synchronizing signals can be separated from the linesynchronizing signals by'applying them -to an integrating circuit, fromwhich responses of different strengths are obtained due to the differentamplitude response to pulses of differing duration. Amplitude separationmay then be successfully used to obtain eld synchronizing" pulses. It isdifficult, however, to secure reliabley operation if the separation ofcolor from field syn-,1 chronizing signals is attempted by the" lsamemeans.

In accordance with the present invention, in-

stead of separating the color synchronizing signal from the fieldsynchronizing signal by direct integration, or by direct frequencydiscrimination, the signals are first applied to a differentiatingcircuit which differentiates the component pulses of the signals toobtain short differentiated pulses of opposite polarity from leading andtrailing edges thereof. Differentiated pulses of one polarity are thenselected to the substantial exclusion of pulses of opposite polarity,for example, by a rectifier or clipping circuit. With appropriateperiodicity and durations of the component pulses of the color and fieldsynchronizing signals, different responses may then be obtained from theselected differentiated pulses corresponding to color and eld signals.In the particular embodiment described hereinafter, separation isaccomplished with the aid of a frequency discriminatingr circuit, sincethe harmonic content of the selected differentiated pulses of the twosignals are sumciently different.

The invention will be more fully understood by the following detaileddescription taken in conjunction with the drawings, in which:

Fig. 1 is a Ycircuit diagram illustrating the invention as incorporatedin a color television receiver; and

Fig. 2 illustrates diagrammatically the wave forms present duringoperation in different parts of the circuit of Fig. 1.

Referring now to the drawings for a more detailed explanation of theinvention, a portion of the synchronizing circuits including the colorsynchronizing signal separation arrangement is shown in Fig. 1. Herecomposite synchronizing signals are applied through a lead l, couplingcapacitor la, and grid resistor lb to the control grid 2 of anelectronic tube 3, here shown as a triode, receiving its anode potentialfrom a common B+ source d. The applied composite synchronizing signalsmay be positive or negative but will here be assumed to be negative.

In the figures, conventional heater-type vacuum tubes have been shown,and the heater windings and power supply omitted from the drawings forthe sake of clarity. The use of a common source of anode potential hasalso been shown conventionally.

All synchronizing signal components of the complete composite televisionsignal may be present at the grid 2. The video is assumed to have beenextracted in previous circuit means forming no part of the presentinvention.

A lead 5 is provided through which the negative composite signal is alsocarried to a circuit, not shown, arranged to extract the verticalsynchronizing pulses. This vertical pulse extraction circuit forms nopart of the present invention.

Tube 3 acts as an inverter and clipper for the composite synchronizingpulses. As shown, it is connected as a grounded load amplifier utilizinga relatively large plate resistor 6 as a D. C. feeder to supply voltageto the tube anode 1. The output of tube 3 is therefore a positivecomposite synchronizing signal across the output A.-C. load resistor 9,which may be relatively small. Coupling capacitor 8 is advantageouslylarge, and may be electrolytic if desired, so that the time constantwith resistors 6 vand 9 is larger than the longest pulses to beamplified. Other types of amplifiers may be employed if desired, thegrounded load type being helpful to reduce distortion.

A portion of the wave form of the positive composite synchronizingsignal at this point has been illustrated schematically in Fig. 2 at A,together with subsequent wave form developments in the circuit whichwill be explained hereafter. Shown are the horizontal synchronizingsignal pulses lll, the vertical synchronizing signal pulse group i i,made up of twelve alternating short portions l2 and long portions I4,and the color synchronizing signal pulse group I5, comprising a seriesof twelve short pulses I6. It will be understood that a linesynchronizing pulse l!) recurs after each line scansion, a vertical oreld synchronizing pulse group Il after each field scansion, and a colorsynchronizing pulse group l5 after each third field in a three-colorsequential system where successive nelds are in different colors.

With the assumed multiplex sound and video signal, sound is transmittedin bursts during the line blanking intervals immediately following theline synchronizing pulses. Inasmuch as the sound bursts must continue tobe transmitted during the field blanking intervals, the field and colorsynchronizing signals contain pulses I2 and IE which have the samespacing as the line synchronizing pulses l0. Thus the sound gate at thereceiver can be maintained in accurate synchronism at all times toprovide accurate separation of sound and video.

In a specific system which has been operated successfully, the linescanning frequency was 31.5 kc., giving a pulse repetition frequency(PRF) of 31.5 kc. for the line synchronizing signal. The narrow andbroad pulses in a single burst of the vertical or iield synchronizingsignal each had a PRF twice the line synchronizing frequency, or 63 kc.,giving an over-all PRF of 126 kc. The eld frequency was 120 elds persecond, so that the bursts of field synchronizing pulses recurred at 120bursts per second. 'The color synchronizing pulses in a single burst hada PRF of 126 kc., and the bursts recurred each third eld or 40 persecond. With different operating standards these figures would of coursebe changed.

Since the eld synchronizing pulses have an over-all PRF of 126 kc..albeit with alternate long and short pulses, there is a considerable 126kc. component. This renders difficult the separation from the 126 kc.color synchronizing pulses by direct frequency separation.

Returning to the circuit of Fig. 1, the positive composite signal withthe form shown in Fis. 2 at A is carried through a lead l1 to soundgate, retrace blanking, and horizontal synchronizing circuits with whichthis application is not concerned.

The composite signal is also fed to a differentiating circuit I9,including capacitor It and resistor l8a, and the output applied to tube2U through a grid resistor 23. The values of the elements of network I9are so chosen that it has a very short time constant, and its outputwill comprise a differential wave having positive and negativedifferentiated pulses corresponding to leading and trailing edges of thecomponent pulses in the applied signal waves. This output is applied tothe control grid 2| of a tube 2U, shown as In Fig. 2 Yat B is show theform of the differential wave appearing at the output of thedifferentiating circuit I9, and the resultant now of anode current intube 20 under the influence of the positive differentiated pulses isillustrated at C. Diierentiated pulse group 5i now represents the fieldsynchronizing signal and group52 the color synchronizing signal.

vIt will be observed that the relative time relationship of the pulsesin group 5l, corresponding to the leading edges of the eld synchronizingsignal Il, is diiferent from that of the pulses in group 52,corresponding to the leading edges of the color synchronizing signal I6.This difference permits obtaining different responses for the two groups5I, 52 of selected differentiated pulses.

The anode circuit of tube 20 contains a tuned network, indicatedgenerally as 25, fed through coupling capacitor 24.

Network 25 is a resonant circuit tuned to yield different outputresponses for the pulse groups 5l and 52. It will be observed that thepulses of group 5| are unevenly spaced, whereas those of group 52 areevenly spaced. Hence tuning to the fundamental frequency of the pulsesof group 52 has been employed with success. Assuming pulses of 126 kc.,for example, currents of this frequency will be able to build up tosubstantial amplitudes,

and others will be discouraged. The separation of the color pulses fromthe vertical pulses will be seen by referring again to Fig. 2.

The vertical and color pulse components have been shown separately fromthe rest of the synchorinizing signals at a and a', respectively, withthe corresponding leading edge differentiated pulses from tube 2Q alinedtherebeneath at c and c'. As a specific illustration, the time at whicheach dilerentiated pulse occurs has been indicated as a percentage ofthe horizontal line period H. The beginning of each long pulse componentof the vertical synchronizing signal is shown as occurring at H or 65% Hafter the beginning of the initial short pulse component. Under c and chave been shown in proper registry at d and d' the form of the ideal 126kc. sine wave currents to which the network 25 is asu sumed tuned.

It will be apparent by comparing c-and d of Fig. 2 that every alternatepulse through tube 28 y produced by the vertical synchronizing signalswill be substantially out of phase with the ideal sine wave, thecorresponding negative peaks of which would occur at 12.5% H, 62.5% H,and so on. Hence it will be seen that current flow in network 25 will bediscouraged from building up in amplitude when the vertical pulses arereceived as illustrated at e.

On the other hand, comparison of c and d will make it apparent thatpulses through tube due to the color synchronizing signal will be inphase with the ideal 126 kc. sine waves,.and so oscillatory currentswill build up through tuned circuit to substantial amplitudes, as seenat e. In practice a ratio of 3 to 1 or better has been obtained betweenthe amplitudes shown at e due to the color pulses, and those shown at edue to the field pulses.

The output of the tuned circuit 25 is applied through a couplingcapacitance 26 to a rectifier 21. Rectifier 21 is shown as a doublediode so connected that its output is proportional to the peak to peakvoltage across the tuned circuit V25.' The output appears across theresistor 28 and shunt capacitor 28a. Capacitor 28a is Ychargedthroughthe diode 21 to nearly the peak to peak voltage'rof the inputwavee. Shunting resistor 28v provides a discharge path for capacitor 28aand the time constant is advantageously selected to smooth the rectifiedoutput of diode 21, but allow'sufciently quick decay at the end of eachpulse group. Fig. 2 at f' illustrates the peak-topeak rectification ofwave e in dotted lines, and the smoothed output wave across capacitor28a at 53. Thus the group of pulses l5 vforming the color synchronizingsignal is converted to a single pulse 53. A similar smoothed wave isformed from wave e for the eld synchronizing signal, but of 'muchsmaller amplitude than Wave 53.

The smoothed output of rectier 21 is then applied through a couplingcircuit, indicated generally as 29, to a tube 3D, here shown as atriode. biased to act as a clipper between the amplitude levels due tothe two types of signals. The response due to the color pulses only willbe per-l mitted to pass through tube 30 and cathode coupling circuit 3|to the output terminal 32. 'Ihe response due to the field synchronizingpulses will be eliminated by the clipping action. Suitable means, notshown in the figures, maythen be utilized for the synchronizing of therotation of the color filter by means of the color synchronizing pulses.

Returning to the tuned circuit 25, it may be seen that it is notessential to have low loss circuit el'ements. Theoretical considerationsshow that a certain optimum Q-factor will produce the maximum diierenceof response to two groups of pulses of different wave form and oilimited duration. -In the practical application of this circuit, optimumdamping of the resonant circuit may be obtained by adjusting plateresistor I3. If desired, a resistor shunting the resonant circuit 25could be employed for damping.

' Resonant circuit 25 has been described specically as tuned to therepetition frequency of the selected differentiated pulses shown in Fig.2 at c'. It may-be desirable in'many cases to tune the circuit to otherfrequencies, particularly higher harmonics than the fundamental, theterm harmonic being used to include the fundamental. The choice dependson the relative time relationships of the selected differentiatedpulsesof the Vsignals to be separated. In any specific instance, theappropriate frequency which will give best discrimination between twoapplied signals may readily be determined. The Fourier analysis of thesignals to be separated is a helpful guide in the selection of the bestfrequency to employ.

It is also apparent that in the circuit of Fig. 1 i

differentiated pulses corresponding to the line synchronizing signalwill also be applied to the tuned circuit 25. With the assumed 31.5 kc.line frequency and 126 kc. for the tuned circuit, the circuit is tunedto the fourth harmonic of the line frequency. The Fourier analysis ofthe differentiated pulses corresponding to the line synchronizing signalmay be taken into account along with the analyses of the eld and colordif-` ferentiated pulses in determining the best frequency for the tunedcircuit. For example, in specific cases, tuning to the second or thirdharmonies of the color synchronizing pulses has been found advantageous.

As shown in Fig. 2 at C, the selected diiferentiated pulses of the colorsynchronizing signal, group r52, are evenly spaced. Generally speaking,this is not necessary, as long as the time relation- 7.'. ships of thepulses are suiiicientlyidierent vfrom the other signal or signals to beseparated.

Also, the positive differentiated pulses of Fig. 2B were selected in therectifier or clipping stage 20. As is apparent from Fig. 2B, thenegative differentiated pulses of the field signal have a relative timerelationship similai1 to the positive diierentiated pulses. The same istrue of the color signal. Hence the negative pulses could have beenselected, if desired, and appropriate means employed to obtain differentresponses from the two series of pulses. Such similarity betweenpositive and negative diierentiated pulses of a given signal may notalways exist, since it depends on the periodicity and length of thepulses in the signal which is differentiated. Generally speaking,`either the leading or trailing pulse edges of one wave should have arelative time relationship different from corresponding pulse edges ofthe other. If, for example, the leading edges of two signals had similartime relationships and the trailing edges different, the differentiatedpulses corresponding to the trailing edges should be selected. This iseasily accomplished by selecting the proper polarity .of differentiatedpulses. If both leading and trailing edges of two signals have diierenttime relationships, it is usually advantageous to select the polarity ofdifferentiated pulses which will yield the greatest dierence between thesignals to be separated, so as to facilitate the production of differentresponses therefrom.

The foregoing disclosure describes the invention as applied to theseparation of color synchronizing signals from eld synchronizing signalsin a color television system, for which the invention is particularlyadapted. While espe-s cially useful at the receiver, it may also beemployed at the transmitter end.

In its broader aspects the invention may 'be applied generally to theproduction of d-ierent responses from diiierent signal waves in acomposite signal, particularly pulse signal waves in which the leadingor trailing pulse edges of one wave have a relative time relationshipldifferent from corresponding pulse edges of another. The invention isespecially useful in connection with pulse signal waves which, whilebearing the time relationship just mentioned, have-frequency andamplitude characteristics, or harmonic contents, sufiiciently similar torender separation by frequency discrimination difficult.

It will be apparent to those in the art that many diierent circuitarrangements may be einn ployed within the scope of the invention, andmodifications made to fit the speciiic requirements.

I claim:

l. In a television system for receiving a composite signal including aplurality of synchroniz-i ing signal waves of different pulsecharacteristics, apparatus for producing different responses from saidsynchronizing signal Waves which comprises means for differentiating thepulses of said synchronizing signal waves to obtain short difierentiatedpulses of opposite polarity from leading and trailing edges thereof,means for rectifying the diierentiated signal waves to selectdifferentiated pulses of one polarity to the substantial exclusion ofpulses of opposite polarity, and filter means for producing differentresponses from the rectified waves.

2. In a television system for receiving a composite television signalincluding a plurality of synchronizing signal waves of different pulsecharacteristics, apparatus for producing different responses from saidsynchronizing signal waves which comprises a differentiating circuit fordifferentiating the pulses of said synchronizing signal waves to obtainshort differentiated pulses of opposite polarity from leading andtrailing edges thereof, a rectifying circuit for rectifying thedifferentiated signal waves to select differentiated pulses of onepolarity to the substantial exclusion of pulses of opposite polarity,discriminating means for producing different responses from therectified waves corresponding to different signal Waves, and means forseparating the different responses.

3. In a television system for receiving a composite television signalincluding a plurality of synchronizing signal waves of different pulsecharacteristics, apparatus for producing a response from onesynchronizing signal wave separate from another which comprises adifferentiating circuit for differentiating the pulses of saidsynchronizing signal waves to obtain short dierentiated pulses oiopposite polarity from leading and trailing edges thereof, a rectifyingcircuit for rectifying the differentiated signal waves to selectdiierentiated pulses of one polarity to the substantial exclusion ofpulses of opposite polarity, a discriminating circuit for producingdifferent responses from the rectified waves corresponding to differentsignal waves, a rectifying circuit for producing rectified responsesfrom said different responses, and a clipping circuit supplied with saidrectied responses to separate at least one rectified response fromanother.

4. In a television system for receiving a composite television signalincluding a plurality of synchronizing signal waves of diierent pulsecharacteristics, apparatus for producing dierent responses from saidsynchronizing signal waves which comprises a differentiating circuit,means for supplying said plurality of synchronizing signal waves to saiddifferentiating circuit to thereby obtain short dierentiated pulses ofopposite polarity from leading and trailing edges of the componentpulses thereof, means for selecting differentiated pulses of onepolarity to the substantial exclusion of pulses of opposite polarity,and a discriminating circuit supplied with the selected pulses foryielding diierent outputs for selected pulses corresponding to onesynchronizing signal wave and selected pulses of another.

5. In a ltelevision system for receiving a come pcsite television signalincluding a plurality of synchronizing pulse signal waves, the leadingor trailing pulse edges of one Wave having a relative time relationshipdierent from corresponding pulse edges of another, apparatus forproducing different responses from said synchronizing signal waves whichcomprises a differentiating circuit,l means for supplying said pluralityof synchronizing signal waves to said differentiating circuit to therebyobtain short diierentiated pulses of opposite polarity from leading andtrailing edges of the component pulses thereof, means for selectingdifferentiated pulses of one polarity corresponding to pulse edgesbearing said different time relationships to thesubstantial exclusion ofdifferentiated pulses of opposite polarity, and a frequency responsivecircuit supplied with the selected differentiated pulses and tuned todiscriminate between selected pulses corresponding to one synchronizingsignal wave and selected pulses of another.

6. Ina television system for receiving' a com' Y v c tial erclusion-ofldifferentiated pulsesv fof -differentiatedpulses to the substanf'-of opposite polarity, a -resonantcircuit supplied VwithV the selecteddifferentiatedpulses` and tuned toY discriminate between selected pulsescorresponding to the color synchronizing signal and selected pulsesofthe other, arectifying and smoothing circuit supplied from the outputof said resonant 'circuit-to obtain different amplitude smoothed signalscorresponding to the color and field synchronizing signals, `and. Vaclipping circuit supplied from said rectifying and smoothing circuit andadapted to passthe smoothed signal corresponding to the colorsynchronizing signal and substantially eliminate the other.

13. In a color television system for receiving ay color televisionsignal including field synchronizing signals of alternate short and longpulses recurring between successive eld scansions and colorsynchronizing signals of short pulses of substantially the same .pulserecurrence frequency recurring sequentially between predetermined fieldscansions, apparatus for producingv a separate color synchronizingresponse which comprises a differentiating circuit, means for supplyingsaid field and color synchronizing signals to said differentiatingcircuit to obtain shortv differentiated 'pulses of opposite polarityfrom leading and trailing edges of the component pulses thereof, meansfor selecting differentiated pulses ofv one polarity to the substantialexclusion of differentiated pulses of opposite po-` larity, a resonantcircuit supplied with the selected differentiated pulses and tuned todiscriminate between pulses corresponding to the color synchronizingsignal and pulses corresponding to the field synchronizing signal, meanssupplied with the output ofthe resonant circuit for producing smoothedresponses of different magnitude corresponding to color and eldsynchronizing signals, and means for separating the smoothed responsecorresponding to the color synchronizing signal from the responsecorresponding to the field synchronizing signal.

14. In a color television system for receiving a colorjtelevision signalincluding fleld synchronizing signals of alternate short and long pulsesrecurring between successive field scansions and color synchronizingsignals of short pulses of substantially the same pulse recurrencefrequency recurring sequentially between predetermined eld scansions,apparatus for producing a separate color synchronizing response whichcomprises a differentiating circuit, means for supplying said field andcolor synchronizing signals to said differentiating circuit to obtainshort differentiated pulses of opposite polarity from leading andtrailing edges of the component pulses thereof, a rectifier forselecting differentiated pulses of one polarity to the substantialexclusion of differentiated pulses of opposite polarity, a resonantcircuit supplied with ytheV selected differentiated pulses and tuned todiscriminate between pulses corresponding to the color'fsfynchro'nizin'g signalv and pulses s' corresponding to 4the fieldsynchronizingsignal; a peak-to-peak 'rectifier and smoothingcircuitsuppliedlfromthe output of the resonant circuit to obtain differentamplitude .smoothed responses corresponding v.to said color and fieldsynchronizing signals, anda clipping circuit supplied-from saidrectifier -r and smoothing circuit adapted to pass the smoothed responsecorresponding to the color synchronizingsignal and substantiallyeliminate theoth'er. 15. ina system for receiving a'composite-si'g'- nalincluding a plurality ofpulse signal wavesfof different' pulsecharacteristics, apparatus for producing different responses from saidpulse'signal waves which comprises-a diiferentiating'fcircuit fordifferentiating said pulse signal W'a'ves to obtain short differentiatedpulses of oppositepolarityfrom leading and trailing edges of thecoinponent pulses thereofpa rectifying circuit :for rece tifying thedifferentiated pulse signal waves to select differentiated pulses of onepolarity `to the substantial exclusion of pulses of opposite-polarit'y,',and a discriminating circuit for 'producingdifferentresponses from the rectiiiedwaves.

16. In a system for yreceiving a coinpositesig nal including a pluralityof pulse signal waves of different pulse characteristics, apparatus forproducing different responses from said pulse signal waves whichcomprises a" differentiating circuit for differentiating saidpulsesignal waves to obtain :short 'differentiatedpulses ofr opposite po,-larity from leading anditr'ailing edges of the component pulsesth'ereof,a rectifying circuit for rectifying the differenti ted Apulse signalwaves to select differentiated pulses of one polarity to the substantialexclusion of pulses of opposite polarity, a 'frequency discriminating'circuit forr producing different amplitude responses from the rectifiedWaves, and an amplitude selective circuit 'for separating the-differentresponses:

17; In a system for receiving a composite signal including a pluralityof pulse signal waves, theleading or trailing edges of the componentpulses of different'signal vWaves bearing different time relationships,apparatus for producing different responses from said signal waves whichcomprises a differentiating circuit; means for supplying said pluralityof pulse signal waves to said differentiating circuit to `obtain shortdifferentiated pulses of opposite polarityfrom leading and trailingedges of the component pulses thereof, a rectifying circuit or selectingone polarity of dif-j ferentiated pulsesv corresponding to pulse edgesbearing said different time relationships to the substantial exclusionof'diiferentiated pulses of opposite polarity, and a filter circuitsupplied With`the selected differentiated pulses and tuned tovdiscriminate between selected pulses corresponding to' one signal waveand selected pulses of' another.

18. In a system for receiving a composite sig--` nal including aplurality of sequentially occurring pulse signal waves, the leading ortrailing edges of the component pulses of one signal 'wave'having arelative 'time relationshipfdifferent from. corresponding edgesfofanother signal'wave, api paratu's for producing different responsesfrom' said signal waves which comprises a differentiating circuit,means' for supplying vsaid lplurality.'V of pulse signal waves to saiddifferentiating cir-j cuit to obtain short differentiated pulses ofopposite polarity from leading and trailing edges' f. the componentpulses thereof, a recti'fying circuit forI selecting onepolarity ofdiiferentated'pulses crrespodmg to'puise" edges bearing' 'said'diserposite television signal including a pluralityof synchronizingpulse signal waves, the leading or trailing pulse edges of one signalwave having a relative time relationship different from correspondingpulse edges of another, apparatus for producing different responses fromsaid synchronizing signal waves which comprises a differentiatingcircuit, means for supplying said plurality of synchronizing signalwaves to said differentiating circuit to thereby obtain shortdifferentiated pulses of opposite polarity from leading and trailingedges of the component pulses-thereof, a rectifying circuit forselecting differentiated pulses of one polarity corresponding to pulseedges bearing said different time relationships to the substantialexclusion of differentiated pulses of opposite polarity, a frequencyresponsive circuit supplied with the selected differentiated pulses andtuned to discriminate between selected pulses corresponding to onesynchronizing signal Wave and selected pulses of another, a rectifyingcircuit for producing rectified signals from the output of saidfrequency responsive circuit, and an amplitude selective circuit forseparating the rectified signal corresponding to one synchronizingsignal wave from another.

'7. In a television system for receiving a composite television signalincluding a plurality of sequentially occurring synchronizing pulsesignal waves, the leading or trailing pulse edges of one f signal wavehaving a relative time relationship different from corresponding pulseedges of another, apparatus for producing different responses from saidsignal Waves which comprises a differentiating circuit, means forsupplying said plurality of synchronizing signal waves to saiddifferentiating circuit to thereby obtain short differentiated pulses ofopposite polarity from leading and trailing edges of the componentpulses thereof, a rectifier for selecting one polarity of differentiatedpulses corresponding to pulse edges bearing said different timerelationships to the substantial exclusion of differentiated pulses ofopposite polarity, a resonant circuit supplied with the selecteddifferentiated pulses and tuned to discriminate between selected pulsescorresponding to one synchronizing signal wave and selected pulses ofanother, a rectifying circuit for rectifying the output of said resonantcircuit to obtain different amplitude responses corresponding to saidone and said other synchronizing signal waves, and an amplitudeselective circuit for separating said different responses in accordancewith their amplitudes to obtain a response corresponding to onesynchronizing signal wave with the substantial elimination of saidother.

8. In a color television system for receiving a color television signalincluding pulsed fieldsynchronizing signals and pulsed colorsynchronizing signals, apparatus for producing dierent responses fromsaid synchronizing signals which comprises a differentiating circuit,means for. supplying said iield and color synchronizing signals to saiddifferentiating circuit to thereby obtain shortdifierentiated pulses ofopposite polarity from leading and trailing edges of the componentpulses thereof, means for selectingV differentiated pulses of onepolarity to the substantial exclusion of differentiated pulses ofpposite polarity, and a discriminating circuit supplied with theselected differentiated pulses for yielding different outputs forselected pulses corresponding to the color and field synchronizingsignals. Y Y i 9..In a color vtelevision system for receiving'a colortelevision'signal including pulsed field Vsynchronizing signals andpulsed color synchronizing signals, apparatus for producing differentresponses from said synchronizing signals which comprises adifferentiating circuit, means for supplying said field and colorsynchronizing signals to said differentiating circuit to thereby obtainshort differentiated pulses of opposite polarity from leading andtrailing edges of the component pulses thereof, a rectifying circuit forselecting differentiated pulses of one polarity to the substantialexclusion of differentiated` pulses of opposite polarity, a frequencyresponsive circuit supplied with the selected'dierentiated pulses andtuned to discriminate between selected pulses corresponding to onesynchronizing signal and selected pulses of the other, and meanssupplied with the output of said frequency responsive circuit forproducing a synchronizing response corresponding to said onesynchronizing signal to the substantial exclusion of said other.

10. In a color television system for receiving a composite colortelevision signal including pulsed eld and color synchronizing signals,the leading or trailing pulse edges of one signal having a relative timerelationship different from corresponding pulse edges of the other,apparatus for producing different responses from said synchronizingsignals which comprises a differentiating circuit, means for supplyingsaid field and color synchronizing signals to said' differentiatingcircuit to obtain short differentiated pulses of opposite polarity fromleading and trailing edges of the component pulses thereof, a rectifierfor selecting differentiated pulses of one polarity corresponding topulse edges bearing said different time relationships to the substantialexclusion of differentiated pulses of opposite polarityfa filter circuitsupplied with the selected differentiated pulses and tuned todiscriminate between selected pulses corresponding to one synchronizingsignal and selected pulses of the other, a rectifier circuit suppliedfrom the output of said Vfilter circuit, and a clipping circuit suppliedfrom said rectier circuit and adapted to pass the rectified outputcorresponding to said one synchronizing signal and substantiallyeliminate the rectified output corresponding to said other.

11. In a color television system for receiving a color television signalincluding pulsed field synchronizing signals recurring betweensuccessive field scansions and pulsed color synchronizing signalsrecurring sequentially between predetermined field scansions, apparatusfor producing a separate color synchronizing response which comprises adifferentiating circuit, means for supplying said field andl colorsynchronizing signals to said differentiating circuit to thereby obtainshort 'differentiated pulses of opposite polarity from leading Aandtrailing edges of thev component pulses thereof, a rectifying circuitfor selecting differentiated pulses of one polarity to the substantialexclusion of differentiated .pulses of opposite polarity, a tunedcircuitsupplied with the selected differentiated pulsesfordiscriminating between selected pulses corresponding to the colorsynchronizing signal and selected pulses of the field synchronizingsignal, andan amplitude selective circuit supplied with the output ofsaid tuned circuit for producing a synchronizing response correspondingto the color synchronizing signal to the substantial exclusion of theresponse. of the field synchronizing signal.

12. In a color television system for receiving a color Ytelevisionsignal including pulsed field ent time relationships to the substantialexclusion of diierentiated pulses of opposite polarity, a resonantcircuit supplied with the selected differentiated pulses and tuned todiscriminate between selected pulses corresponding to one signal Waveand selected pulses of another, a rectifying circuit for rectifying theoutput of said resonant circuit to obtain different amplitude responsescorresponding to said one and said other signal waves, and an amplitudeselective circuit for separating said dilerent responses in accordancewith their amplitudes to obtain a response corresponding to one signalwith the substantial elimination of another.

19. In a television system, the method of producing different responsesfrom a plurality of pulse'synchronizing signals in a composite signalwhich comprises differentiating said pulse synchronizing signals toobtain short diierentiated pulses of opposite polarity from leading andtrailing edges of the component pulses thereof= rectifying thedifferentiated signals to select diilerentiated pulses of one polarityto the substantial exclusion of pulses of opposite polarity, and n1-tering the rectified signals to produce different responsescorresponding to different synchronizing signals.

20. In a color television system having pulsed field and colorsynchronizing signals in a composite color television signal, the methodof producing different responses for said synchronizing signals whichcomprises dilerentiating said synchronizing signals to produce shortdifferentiated pulses of opposite polarity from leading and trailingedges of the component pulses thereof, selecting differentiated pulsesof one polarity to the substantial exclusion of pulses of oppositepolarity, and filtering the selected diierentiated pulses to producedilerent responses corresponding to color and field synchronizingsignals,

21. In a color television system having pulsed eld and colorsynchronizing signals in a composite color television signal, the methodof producing diflerent responses for said synchronizing signals whichcomprises differentiating said synchronizing signals to produce shortdillerentiated pulses of opposite polarity from leading and trailingedges of the component pulses thereof, rectifying the differentiatedsignals to select differentiated pulses of one polarity to thesubstantial exclusion of pulses of opposite polarity, ltering theselected differentiated pulses to produce different magnitude outputscorresponding to color and eld synchronizing signals, and separatingsaid outputs in accordance with their magnitudes to yield a seperatesynchronizing response for one of said synchronizing signals.

KURT SCHLESINGE'R.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,198,969 Lewis Apr. 30, 19402,229,964 Dome Jan. 28, 1941 2,319,789 Chambers May 25, 1943 FOREIGNPATENTS Number Country Date 524,286 Great Britain Aug. 2, 1940 555,492Great Britain Aug. 25, 1943

